Manhole cover



C. F. AVILA MANHOLE COVER June 29, 1954 2 Sheets-Sheet 1 Filed Nov. 3, 1950 C. F. AVILA MANHOLE COVER June 29, 1954 2 Sheets-Sheet 2 Filed Nov. 3, 1950 Patented June 29, 1954 UNITED STATES PATENT oFFlcE MANHOLE COVER Charles F. Avila, Milton, Mass.

Application November 3, 1950, Serial No. 193,993

The present invention relates to manhole covers and particularly to means for locking manhole covers in place.

Heretofore in the covering of manholes, it has been the practice simply to place the manhole cover1 on top of the manhole frame and to rely on the weight of the cover itself to prevent its being dislodged. However, explosions from underground sources Occasionally occur with such force as to project the cover to considerable heights with hazard of damage to life and property. These explosions result mainly from accumulations of gas from any of several sources. The gas may form an explosive mixture with the air in the manhole and the mixture is subject to detonation on the presence of a spark or flame.

Various expedients have been suggested for preventing accidents of this nature and many have followed the theory of providing a spring mounting for the covers. These are usually either excessively massive and costly or ineffective and I have discovered that the reason therefor is that the cover under the initial impact of the explosion acquires such a considerable kinetic energy before compressing the spring that it tends to tear away the supporting structure.

According to the present invention I provide a manhole cover which will be firmly secured and capable of withstanding the high explosion pressures without movement and also to permit the release of gas pressure therethrough. The cover of the present invention is of simple form adaptable to manholes of existing constructions.

In the accompanying drawings Fig. 1 is a sectional elevation of the manhole and manhole frame taken along line I-l of Fig. 2; Fig. 2 is a top view of the manhole; Fig. 3 is a top View of the manhole cover; Fig. 4 is a bottom plan view of the manhole cover; Fig. 5 is a sectional elevation of the manhole with the cover in locked position; Fig. 6 is a face view of one of the holding blocks showing the locking shaft in locking position; and Fig. 7 is an isometric View of the operating arm and shaft in the locked position.

In the illustrated embodiment of the invention the manhole I0 is provided with the usual manhole frame I2, which is flush with the road surface as indicated in Fig. 1. The frame is provided with an annular seat I4to receive the cover. As shown in Fig. 1 the walls of the frame I2 taper toward the top. On diammetrically opposite p-arts of the frame and partway down the walls are secured two locking blocks I6 and I8.

The block I6 is of simple overhung construc- 1 Claim. (Cl. 94-35) tion as shown in Fig. 1. The block I8, as shown in Fig. 6, has one part of the bottom surface formed on the arc of a circle 2t to conform to the movement of a locking shaft as Will be presently described.

The manhole cover 22 shown in Figs. 3 and 4 is of circular form to rest on the seat I4 and is preferably provided with positioning notches 24 to register with pins 26- in the seat I4. The cover is formed with a large number of slots 21 for ventilation to reduce gas accumulation and to relieve the gas pressure in the event of an explosion in the manhole. Secured to the under side of the cover are two blocks 28 and 3D. The block 28 is of a contour to conform to the shape of the cover and is provided with a lip to underlie the overhanging part of the stationary block I6. The construction is such that the cover may be put in place by tipping it slightly so that the lip of the block 28 slides under the overhang of the block I6.

The block 30 is arranged to lie immediately adjacent to the crank engaging block I8 on the frame. The block 3D has a yoke 3I in which is journaled a crank 32, the free endof which is adapted to ride under the curved portion 20 of the block I8. Fig. 6 shows the free end or locking portion of the crank 32 in the locked position. In this position, it rests against an abutment I 8a formed in the block I8 adjacent the horizontal lower portion of the arcuate bottom surface 20. The locking portion of the crank engages the horizontal portion of the surface 20 while bearing against the abutment Illa.

It will be understood that the under side of the cover may be provided with vertical strengthening ribs, two of Which are shown at 33 in Fig. 4 and in broken-away form in Fig. 5. These ribs are of any suitable shape, according to usual cover design practices. The blocks 28 and 30, as indicated in Fig. 5, are of such shapes as to conform to the contours of the ribs. The blocks are secured to the cover by any suitable means, preferably by bolting.

An operating arm 34 is secured to the inner end of the crank 32 and is received in one of the slots 2l of the cover. The arrangement of the arm is such that when it is seated in its slot the crank 32 is in locking position under the end of the curved portion 20 of the block I8. To unlock the cover it is only necessary to pry up the arm 34 to vertical position thereby swinging the end of the crank 32 out from under the block I8, whereupon the cover may be lifted. In replacing the cover, the arm 34 is in raised position, the cover is tilted into position as above described with the positioning notches 24 in their proper places, and aiter the cover is seated, the handle or arm 34 is simply pressed down into the slot, thereby rmly locking the cover in place. The parts are so arranged that the arm 34 rotates in direction of traiiic. If by error the arm 34 is left in its vertical position or if it becomes dislodged for any reason, the force of a wheel riding over it will press it down into locking position.

The lock effected by the blocks I6 and 28 in one side and the block I3 and crank 32 on the other side resists movement of the cover even under the most severe explosions. I have discovered that even with a solid cover the parts are not dislodged by the most serious explosions and the worst result is simply to lift or dislodge the frame I2 so that the gas pressure dissipates under the road surface. However, by provision of the slots 2l by which about three-fourths of the area of the cover may be open, the force of the blast is largely dissipated without any damage even to the manhole frame. It has also been found that smoke may issue from the openings for some time prior to the blast and thus` give a visual warning of danger so that pedestrians may keep away. In any event, the rm holding of the cover to frame is essential, since even with slotted cover, any yielding, as by the use of springs, will allow the cover to acquire suflicient kinetic energy to result in excessive damage to the frame. The present invention provides for such holding action, while still permitting ready removal of the cover for access to the manhole.

Having thus described the invention, I claim:

The combination of a manhole frame having securing blocks extending inwardly at substantially opposing points thereof, said blocks including a crank engaging block having an arcuate bottom surface with a horizontal lower portion and an abutment adjacent to said portion, and a cover for the frame, said cover having a supporting block underlying a securing block when the cover is seated by lowering it upon the frame from a tilted position, a journal block lying adjacent to the crank engaging block when he cover is fully seated, a crank supported in t e journal block for rotation about a horizontal axis disposed beneath the surface of the cover, said crank having a locking portion passing under said arcuate surface and locking the cover by engaging said horizontal portion of the surface while bearing against said abutment, and an operating arm secured to the crank in position to be rotated upwardly through an elongated opening in the cover, said arm and the locking portion of the crank being in such relative positions that said locking portion is against said abutment when the arm is depressed below the surface of the cover and free of said arcuate surface when the arm is raised through said opening.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 670,506 Dent Mar. 26, 1901 1,127,116 Thorne Feb. 2, 1915 1,694,133 McHugh Dec. 4, 1928 1,712,267 Gsohwind May 7, 1929 1,988,360 Moore Jan. 15, 1935 2,511,425 Beauchamp June 13, 1950 FOREIGN PATENTS Number Country Date 380,160 Great Britain Sept- 15, 1932 

